1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing a semiconductor device.
2. Description of the Related Art
Light-emitting diodes and other semiconductor light-emitting devices are manufactured by forming semiconductor layers or layered structure including an n-layer, an active layer, a p-layer on a growth substrate such as a sapphire substrate, and forming electrodes on the growth substrate and the surface of the semiconductor layer. Part of the semiconductor layer is etched away using reactive ion etching or another technique to expose the n-layer and form electrodes on the n-layer and p-layer, respectively.
Semiconductor light-emitting devices are increasingly efficient and have higher output through recent technological advances. However, the amount of heat produced in the semiconductor light-emitting devices has also increased together with the higher output, which causes problems such as decreased light-emission efficiency and decreased reliability of the semiconductor light-emitting device through, for example, degradation of the semiconductor layer. In order to solve the problems, a configuration is used in which the growth substrate having relatively low thermal conductivity is removed, and the semiconductor film or layered structure is supported by a metal having relatively high thermal conductivity instead. Heat dissipation of the semiconductor light-emitting device is improved by adopting such a structure, and improvement in light-emission efficiency, more particularly, light extraction efficiency can be expected by removing the growth substrate. In other words, it is possible to reduce light absorption that occurs when light passes through the growth substrate, and to reduce total reflection light occurring at the interface between the semiconductor film and the growth substrate due to the refractive index difference. It is a general practice to remove the growth substrate using a laser lift off (LLO) method.
Japanese Laid-open Patent Application No. 2000-228539 (hereinafter referred to as Patent Reference 1) discloses a manufacturing process of a light-emitting device wherein a semiconductor epitaxial layer is formed on a growth substrate via an amorphous nitrogen compound semiconductor layer. Patent Reference 1 discloses a process in which the growth temperature is set to 600° C. or less and the supply ratio of a group III element with respect to a V group element is set to 1000 or less when an amorphous nitrogen compound semiconductor layer is grown by vapor phase deposition to thereby form voids within the amorphous nitrogen compound semiconductor layer, and that the growth substrate, in some cases, is naturally separated from the semiconductor epitaxial layer.